lib: more nuanced file access errors.

Several new more specific exception types are derived from
file-error and used. Error handlers can distinguish unexpected
non-existence, unexpected existence and permission errors
from each other and other errors.

* lib.c (path_not_found_s, path_exists_s, path_permission_s):
New symbol variables.
(obj_init): New variables initialized.

* lib.h (path_not_found_s, path_exists_s, path_permission_s):
Declared.

* parser.c (open_txr_file): Use new errno_to_file_error
function to convert errno to exception symbol.

* socket.c (open_sockfd): Likewise.

* stream.c (open_directory, open_file, open_fileno,
open_command, open_process, run, remove_path, rename_path):
Likewise, and process-error is used in open_process and run
instead of file-error for problems related to creating the
process.

* sysif.c (errno_to_file_error): New function.
(mkdir_wrap, ensure_dir, chdir_wrap, getcwd_wrap, mknod_wrap,
chmod_wrap, symlink_wrap, link_wrap, readlink_wrap, stat_impl,
umask_wrap, ): Use
errno_to_file_error to convert errno to exception symbol.
(exec_wrap): Use process-error instead of file-error.

* sysif.c (errno_to_file_error): Declared.

* unwind.c (uw_init): Register path-not-found, path-exists and
path-permission as subtypes of file-error.

* txr.1: Documented.

1 files changed, 3 insertions, 2 deletions

diff --git a/socket.c b/socket.c
index 7c68b057..79df7b7e 100644
--- a/socket.c
+++ b/socket.c
@@ -770,9 +770,10 @@ static val open_sockfd(val fd, val family, val type, val mode_str)
     FILE *f = (errno = 0, w_fdopen(c_num(fd), c_str(normalize_mode(&m, mode_str, m_rpb))));
 
     if (!f) {
+      int eno = errno;
       close(c_num(fd));
-      uw_throwf(file_error_s, lit("error creating stream for socket ~a: ~d/~s"),
-                fd, num(errno), string_utf8(strerror(errno)), nao);
+      uw_throwf(errno_to_file_error(eno), lit("error creating stream for socket ~a: ~d/~s"),
+                fd, num(eno), string_utf8(strerror(eno)), nao);
     }
 
     return set_mode_props(m, make_sock_stream(f, family, type));